A chemical mechanical polishing (hereinafter, referred to as “CAMP”) or planarizing process is conducted to planarized various kinds of substrates, that is, substrates on which silicon, silicon oxide, metal (tungsten, copper, or titanium), metal oxide, dielectric, or ceramic is deposited, in all stages of a semiconductor process. This polishing process is one of precision/glossy surface grinding processes, in which polishing slurry is supplied between a polishing pad and a wafer to chemically corrode a surface of the wafer and to mechanically polish the corroded surface.
Typically, a polishing pad comprises a polishing pad which has a polishing layer for rubbing an object during a direct polishing process, and a base pad for supporting the polishing pad.
A method of producing the polishing pad is disclosed in, for example, Korean Patent Application Nods. 2001-46795, entitled “a method of producing a chemical mechanical polishing pad using a laser”, 2002-45832, entitled “a method of producing a polishing pad using a laser beam and a mask”, and 2002-06309, entitled “a composition for producing a polyurethane elastic body having high hardness and excellent wear resistance”. Generally, micro-cells are formed, or a through hole or a groove is formed in the polishing pad through physical and chemical methods so as to preserve slurry for a long time. With respect to this, the above Korean Patent Application Nods. 2001-46795 and 2002-45832 disclose a method of forming various patterns of micro-holes, grooves and/or through holes on a polishing pad using a laser and a mask, which is adopted instead of a conventional method of forming cells by the insertion of a hollow body or chemical generation of foam, or instead of another conventional method of forming grooves and through holes using mechanical means. Furthermore, the above Korean Patent Application No. 2002-06309 suggests a composition for producing the polyurethane elastic body, which is capable of improving hardness and wear resistance of the polishing pad.
As well, the base pad is produced by incorporating sheet or felt, which is formed by foaming polyurethane material, into a polymeric substance. In more detail, the production of a polyurethane pad using typical foaming is achieved through a one-shot process consisting of one stage, in which all raw materials and foam bodies (chemical and mechanical foam) are agitated and reacted with each other at the same time, thereby forming fine pores in the pad. In the method of producing the pad through urethane incorporation, fibers, such as felt, are immersed in (whetted by) liquid polyurethane which is previously produced, thus polyurethane fills gaps between the felts, resulting in the formation of fine pores.
Polishing slurry and DAI water used during the polishing process may permeate into the fine pores existing in the base pad, and the permeation into the fine pores may negatively affect polishing uniformity of a wafer, which is an indicate of performance of the CAMP process. Additionally, the permeation reduces the time for which the polishing pad is used, that is, its lifetime. Furthermore, physical properties of the conventional base pad may be changed by a rotational force between a platen and a wafer and vertical stress during the CAMP process.